Clonidine as an adjuvant to prolong local analgesia in conventional scleral buckle surgery

PURPOSE: The aim of this study was to determine the effect of a single dose of 150 μg of clonidine as an adjuvant to levobupivacaine (Chirocaine(®)) in retrobulbar block on postoperative safety and analgesia.

METHODS: This was a prospective, randomized, controlled, double-blind trial. One hundred twenty patients with a rhegmatogenous retinal detachment scheduled to undergo external buckling surgery and cryocoagulation were asked to participate. Participants were randomly assigned either to receive 3-5 mL Chirocaine (22.5-37.5 mg) or 3-5 mL Chirocaine and 1 mL clonidine (150 μg) before surgery. Main outcome measures were postoperative pain, use of analgesics, blood pressure, and plasma clonidine concentration. Nine nonrandomized patients consented to give blood samples for pharmacokinetic analysis.

RESULTS: There was no significant difference in pain score between both groups. On average, the use of analgesic medication occurred later in the clonidine group (P=0.0004), but there was no statistical difference in the first time that postoperative medication was taken (P=0.13). Blood pressure was reduced by clonidine (systolic: P=0.02, diastolic: P=0.006). Clonidine levels could be demonstrated during the 24-h postoperative period, with an average half-life of 22 h.

CONCLUSIONS: Administration of clonidine as an adjuvant to conventional retrobulbar block is safe, and delays the postoperative use of analgesics. The reduction of postoperative pain and the time of first use of analgesic medication, however, were not significantly different between groups. Further, pain scores in both study groups remained low. Therefore, the beneficial effect of clonidine in conventional scleral buckle surgery appears to be limited.